Darin J. Law

University of Arizona

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Co-Authors

David D. Breshears

University of Arizona

Juan Camilo Villegas

Universidad de Antioquia

Jason P. Field

University of Arizona

S. R. Saleska

University of Arizona

G. Barron-Gafford

University of Arizona

Scott C. Stark

Michigan State University

Elizabeth S. Garcia

University of Washington

Imma Oliveras

UMR Botanique et Modélisation de l’Architecture des Plantes et des végétations

Mallory L. Barnes

Indiana University Bloomington

Alysha I. Coppola

ETH Zurich

Cooperative Institutions

Ecological Society of America

117

Purdue University West Lafayette

106

University of Arizona

National Institute of Amazonian Research

Universidade de São Paulo

John Wiley & Sons (United States)

United States Geological Survey

National Institute for Space Research

University of Western Australia

Universidade Federal do Oeste do Pará

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Hydrologic, abiotic and biotic interactions: plant density, windspeed, leaf size and groundwater all affect oak water use efficiency

Ecohydrology (2010)

Darin J. Law Deborah M. Finch

Abstract Plant water use in drylands can be complex due to variation in hydrologic, abiotic and biotic factors, particularly near ephemeral or intermittent streams. Plant use of groundwater may be important but is usually uncertain. Disturbances like fire contribute to complex spatiotemporal heterogeneity. Improved understanding of how such hydrologic, abiotic, and biotic factors affect plant water use is needed not only to address management issues related to land use but also due to climate change, particularly for drylands projected to become warmer and drier such as much of the southwestern USA. Here we focus on the interactive roles of hydrologic, abiotic, and biotic factors in determining plant water use of Gambel oak in ephemeral and/or intermittent riparian areas of ponderosa pine forest in central New Mexico, USA along a fire disturbance gradient with varying oak densities. More specifically, the purpose of this research is to determine: (1) depth to and frequency of groundwater associated with intermittent and ephemeral streams, (2) isotopic indications of whether or not groundwater is used by plants, and (3) plant water use (conductance, transpiration, and water use efficiency) interactions with groundwater. Depth to groundwater, which could be as shallow as 1 m or less, increased with plant density but plant water use efficiency decreased. Photosynthesis:transpiration ratios maximizing water use efficiency for a given successional stage appeared to be also affected by windspeed and leaf size, highlighting interactive effects of hydrologic, abiotic and biotic affects—a finding that may be ecohydrologically relevant for other dryland riparian systems. Published 2010. This article is a US Government work and is in the public domain in the USA.

Ecohydrology

Biotic component

Ephemeral key

10.1002/eco.172

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Citations (2)

Aeolian sediment and dust fluxes during predominant “background” wind conditions for unburned and burned semiarid grassland: Interplay between particle size and temporal scale

Aeolian Research (2014)

Luis Merino‐Martín Jason P. Field Juan Camilo Villegas Jeffrey Whicker David D. Breshears

10.1016/j.aeolia.2014.02.004

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Citations (12)

Beyond greenness: Detecting temporal changes in photosynthetic capacity with hyperspectral reflectance data

PLoS ONE (2017)

Mallory L. Barnes David D. Breshears Darin J. Law Willem van Leeuwen Russell K. Monson

Earth's future carbon balance and regional carbon exchange dynamics are inextricably linked to plant photosynthesis. Spectral vegetation indices are widely used as proxies for vegetation greenness and to estimate state variables such as vegetation cover and leaf area index. However, the capacity of green leaves to take up carbon can change throughout the season. We quantify photosynthetic capacity as the maximum rate of RuBP carboxylation (Vcmax) and regeneration (Jmax). Vcmax and Jmax vary within-season due to interactions between ontogenetic processes and meteorological variables. Remote sensing-based estimation of Vcmax and Jmax using leaf reflectance spectra is promising, but temporal variation in relationships between these key determinants of photosynthetic capacity, leaf reflectance spectra, and the models that link these variables has not been evaluated. To address this issue, we studied hybrid poplar (Populus spp.) during a 7-week mid-summer period to quantify seasonally-dynamic relationships between Vcmax, Jmax, and leaf spectra. We compared in situ estimates of Vcmax and Jmax from gas exchange measurements to estimates of Vcmax and Jmax derived from partial least squares regression (PLSR) and fresh-leaf reflectance spectroscopy. PLSR models were robust despite dynamic temporal variation in Vcmax and Jmax throughout the study period. Within-population variation in plant stress modestly reduced PLSR model predictive capacity. Hyperspectral vegetation indices were well-correlated to Vcmax and Jmax, including the widely-used Normalized Difference Vegetation Index. Our results show that hyperspectral estimation of plant physiological traits using PLSR may be robust to temporal variation. Additionally, hyperspectral vegetation indices may be sufficient to detect temporal changes in photosynthetic capacity in contexts similar to those studied here. Overall, our results highlight the potential for hyperspectral remote sensing to estimate determinants of photosynthetic capacity during periods with dynamic temporal variations related to seasonality and plant stress, thereby improving estimates of plant productivity and characterization of the associated carbon budget.

Photosynthetic capacity

Enhanced vegetation index

Seasonality

10.1371/journal.pone.0189539

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Citations (67)

Diverse anthropogenic disturbances shift Amazon forests along a structural spectrum

Frontiers in Ecology and the Environment (2023)

Marielle N. Smith Scott C. Stark Tyeen Taylor Juliana Schietti Danilo Roberti Alves de Almeida

Amazon forests are being degraded by myriad anthropogenic disturbances, altering ecosystem and climate function. We analyzed the effects of a range of land‐use and climate‐change disturbances on fine‐scale canopy structure using a large database of profiling canopy lidar collected from disturbed and mature Amazon forest plots. At most of the disturbed sites, surveys were conducted 10–30 years after disturbance, with many exhibiting signs of recovery. Structural impacts differed in magnitude more than in character among disturbance types, producing a gradient of impacts. Structural changes were highly coordinated in a manner consistent across disturbance types, indicating commonalities in regeneration pathways. At the most severely affected site – burned igapó (seasonally flooded forest) – no signs of canopy regeneration were observed, indicating a sustained alteration of microclimates and consequently greater vulnerability to transitioning to a more open‐canopy, savanna‐like state. Notably, disturbances rarely shifted forests beyond the natural background of structural variation within mature plots, highlighting the similarities between anthropogenic and natural disturbance regimes, and indicating a degree of resilience among Amazon forests. Studying diverse disturbance types within an integrated analytical framework builds capacity to predict the risk of degradation‐driven forest transitions.

Microclimate

Forest dynamics

10.1002/fee.2590

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Citations (9)

Turbidity maximum in the macrotidal, highly turbid Humber Estuary, UK: Flocs, fluid mud, stationary suspensions and tidal bores

Estuarine Coastal and Shelf Science (2006)

R.J. Uncles John A. Stephens Darin J. Law

Turbidity

Tidal range

Tidal irrigation

10.1016/j.ecss.2005.10.013

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Citations (147)

Biological invasions and climate change amplify each other’s effects on dryland degradation

Global Change Biology (2021)

Sujith Ravi Darin J. Law Joshua S. Caplan G. Barron-Gafford Katerina Dontsova

Climate models predict that, in the coming decades, many arid regions will experience increasingly hot conditions and will be affected more frequently by drought. These regions are also experiencing rapid vegetation change, notably invasion by exotic grasses. Invasive grasses spread rapidly into native desert ecosystems due, in particular, to interannual variability in precipitation and periodic fires. The resultant destruction of non-fire-adapted native shrub and grass communities and of the inherent soil resource heterogeneity can yield invader-dominated grasslands. Moreover, recurrent droughts are expected to cause widespread physiological stress and mortality of both invasive and native plants, as well as the loss of soil resources. However, the magnitude of these effects may differ between invasive and native grasses, especially under warmer conditions, rendering the trajectory of vegetated communities uncertain. Using the Biosphere 2 facility in the Sonoran Desert, we evaluated the viability of these hypothesized relationships by simulating combinations of drought and elevated temperature (+5°C) and assessing the ecophysiological and mortality responses of both a dominant invasive grass (Pennisetum ciliare or buffelgrass) and a dominant native grass (Heteropogan contortus or tanglehead). While both grasses survived protracted drought at ambient temperatures by inducing dormancy, drought under warmed conditions exceeded the tolerance limits of the native species, resulting in greater and more rapid mortality than exhibited by the invasive. Thus, two major drivers of global environmental change, biological invasion and climate change, can be expected to synergistically accelerate ecosystem degradation unless large-scale interventions are enacted.

Native plant

Bromus tectorum

10.1111/gcb.15919

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Citations (37)

In situ characterization of suspended particles using focused-beam, laser reflectance particle sizing

Geological Society London Special Publications (1998)

Darin J. Law A.J. Bale

Abstract Measurements of the size distribution of suspended particles were made as part of the LISP (UK) experiment using a novel, in situ instrument which employs focused-beam, laser reflectance. Data were acquired over three complete, ebb-flood tidal cycles at two stations possessing different elevations on the intertidal mudflat. The reflectance method, which employs a physical arrangement similar to optical back-scatter sensors for measuring the concentration of suspended particulate matter (SPM), measures sediment particles in the size range 2–1000 µm with negligible disruption to fragile aggregates and can operate over the wide range of SPM concentrations found in estuaries. The results indicated that the median sizes ( D 50 ) of particle populations over the intertidal mud flats were relatively constant at 60–100 µm even during mild erosion and resuspension events caused by ebb and flood tides. However, populations with D 50 values of up to 300 μm were seen at one station within the ridge-runnel systems during resuspension. These large aggregates were attributed to the particularly ‘mobile’ sediment in that environment and to increased biodeposition. In general, variations in the size characteristics of particles measured in situ were consistent with the properties of the underlying substrate. Measured sizes compared well with values determined by direct video-microscope observation.

Characterization

Particle (ecology)

10.1144/gsl.sp.1998.139.01.05

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Citations (10)

Candidate halophytic grasses for addressing land degradation: Shoot responses ofSporobolus airoidesandPaspalum vaginatumto weekly increasing NaCl concentration

Arid Land Research and Management (2017)

Mohammad Pessarakli David D. Breshears James L. Walworth Jason P. Field Darin J. Law

In many arid and semiarid regions worldwide, high levels of soil salinity is a key driver of land degradation, as well as a key impediment to re-establishing plant cover. Combating land degradation and erosion associated with soil salinity requires experimental determination of plant species that can grow in soils with high levels of salinity and can be used to re-establish plant cover. Herein, we evaluated the responses of untested candidate cultivars of two halophytic grass species to high soil salinity: alkali sacaton (Sporobolus airoides Torr.) and seashore paspalum (Paspalum vaginatum Swartz). We evaluated the growth responses of both species in a greenhouse under control (no-salt) and various levels of NaCl salinity (EC 8, 16, 24, 32, 40, and 48 dSm−1) using Hoagland solution in a hydroponics system in a randomized complete block design trial. At all salinity levels, sacaton grass had a greater shoot height, shorter root length, lower shoot fresh and dry weights, and poorer color and general quality compared to seashore paspalum. The shoot fresh and dry weights of both grasses were greatest at the low to medium levels of salinity, with the greatest response observed at EC 16 dSm−1. At the highest level, salinity significantly reduced shoot fresh and dry weights of both grasses. Because growth of both halophytic species exhibited high tolerance to salinity stress and were stimulated under low to medium levels of salinity, both species could be considered suitable candidates for re-establishing plant cover in drylands to combat desertification and land degradation associated with high levels of soil salinity.

Paspalum

Dryland salinity

10.1080/15324982.2017.1284944

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Citations (11)

Synergistic Ecoclimate Teleconnections from Forest Loss in Different Regions Structure Global Ecological Responses

PLoS ONE (2016)

Elizabeth S. Garcia Abigail L. S. Swann Juan Camilo Villegas David D. Breshears Darin J. Law

Forest loss in hotspots around the world impacts not only local climate where loss occurs, but also influences climate and vegetation in remote parts of the globe through ecoclimate teleconnections. The magnitude and mechanism of remote impacts likely depends on the location and distribution of forest loss hotspots, but the nature of these dependencies has not been investigated. We use global climate model simulations to estimate the distribution of ecologically-relevant climate changes resulting from forest loss in two hotspot regions: western North America (wNA), which is experiencing accelerated dieoff, and the Amazon basin, which is subject to high rates of deforestation. The remote climatic and ecological net effects of simultaneous forest loss in both regions differed from the combined effects of loss from the two regions simulated separately, as evident in three impacted areas. Eastern South American Gross Primary Productivity (GPP) increased due to changes in seasonal rainfall associated with Amazon forest loss and changes in temperature related to wNA forest loss. Eurasia's GPP declined with wNA forest loss due to cooling temperatures increasing soil ice volume. Southeastern North American productivity increased with simultaneous forest loss, but declined with only wNA forest loss due to changes in VPD. Our results illustrate the need for a new generation of local-to-global scale analyses to identify potential ecoclimate teleconnections, their underlying mechanisms, and most importantly, their synergistic interactions, to predict the responses to increasing forest loss under future land use change and climate change.

Teleconnection

Deforestation

10.1371/journal.pone.0165042

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Citations (51)

Issue Information

Frontiers in Ecology and the Environment (2023)

Songlin Fei Elizabeth A. LaRue K Dahlin Robert J. Fahey Brandon C. Alveshere

Cover picture: Structural diversity plays a critical role in shaping ecosystem patterns and processes.Advances in remote sensing and digital technology, such as drone-based orthophotos (background) and a 3D lidar point cloud (central) derived from a mobile mapping system, allow for structural diversity to be mapped and measured in novel ways, yielding a wide range of new insights in ecology.

10.1002/fee.2520

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Citations (0)